The present invention relates to a method for the preparation of tertiary-hydrocarbylsilyl compounds, and, more particularly, relates to a method for the preparation of tert-hydrocarbylsilyl compounds through a Grignard reaction.
The following methods are known for the preparation of tert-hydrocarbylsilyl compounds:
(1) the reaction of tert-alkyllithium with chlorosilanes, and
(2) in an improvement of the preceding method, the reaction of a tert-alkyl Grignard reagent with chlorosilanes (Japanese Patent Application Laid Open, Kokai, Number 60-222492, 222,492/85, and Japanese Patent Application Laid Open Number 60-237092, 237,092/85).
However, method (1) is associated with the following problems, which serve to make production on an industrial scale fairly difficult.
1. Generation of the starting tert-alkyllithium entails the preparation of a highly active lithium microdispersion at high temperatures (approximately 200 degrees Centrigrade), which must then be reacted with a tert-alkyl halide using pentane solvent (low-boiling hydrocarbon) in an argon current. These circumstances demand careful attention with regard to reaction management, and the reaction must be run in a special vessel.
2. The obtained tert-alkyllithium is a very hazardous reagent which will autoignite merely upon contact with the atmosphere.
In the case of method (2), a tert-alkylchlorosilane is obtained by the reaction of a tert-alkyl Grignard reagent with SiH-containing (low sterically hindered) chlorosilanes such as trichlorosilane or methyldichlorosilane, or by the reaction of a tert-alkyl Grignard reagent with a disilane such as dimethyltetrachlorodisilane or hexachlorodisilane. Considering, for example, the use of this synthetic method to prepare the practically useful silylating agent, tert-butyldimethylchlorosilane, the reaction of methyldichlorosilane and a tert-butyl Grignard reagent presents itself. However, because the product here is tert-butylmethylchlorosilane, the residual chlorine group must be methylated by reaction with a methyl Grignard reagent and the SiH group must finally be chlorinated with chlorine in order to obtain the desired tert-butyldimethylchlorosilane. Moreover, in the case of the reaction of dimethylchlorosilane with a tert-butyl Grignard reagent, the SiH group must be chlorinated with chlorine in order to obtain the desired tert-butyldimethylchlorosilane (Japanese Patent Application Laid Open Number 60-222492). In the case of the reaction of hexachlorodisilane with a tert-butyl Grignard reagent, a partial methylation is necessary to obtain tert-butyldimethylchlorosilane (Japanese Patent Application Laid Open Number 60-237092). Thus, the former method suffers from a lengthy synthetic route, while the latter method requires special disilanes and, moreover, utilizes only half of the silicon.
Accordingly, the object of the present invention is a solution to the preceding defects encumbering the prior art based on the introduction of a simple, high-yield method for the preparation of tert-hydrocarbylsilyl compounds.
The method of the present invention provides for the simple, high-yield preparation of the desired tert-hydrocarbylsilyl compounds. As a particular matter, the preparative method of the present invention offers the advantage of the facile, high-yield preparation by a single-step reaction of tert-hydrocarbylsilyl compounds such as tert-butyldimethylchlorosilane which are extremely useful as silylating agents and are effectively used in the synthesis of steroids, prostaglandins, and so forth.